Riding high: Greek heiress Athina Onassis puts on a good show at Equestrian Centre in Italy

Dressed for business in her horse-riding gear, it isn't immediately obvious that Athina Onassis iss one of the world's most prominent heiresses.

But the 28-year-old is the only surviving relative of Aristotle Onassis, the Greek shipping magnate, and heir to a huge fortune.

Casual: the show-jumping heiress was dressed down for the event

The blonde heiress who has been a keen equestrian since she was a teenager was in Italy with her husband for a show.

She began dating Brazilian professional showjumper and two-time Olympic medalist Alvaro Miranda Neto, more commonly known as "Doda", in March 2003, and moved to São Paulo, where the couple now live.

Impressive: Athina has been a keen equestrian since she was a teenager

Miranda and Onassis were married in December 2005, after which she assumed a hybrid version of the Onassis and Miranda names, and dropped the Roussel name. According to reports, the wedding guests consumed 1000 bottles of champagne.

The 28 year-old looked relaxed and casual in her all white outfit, clearly designed to make her as streamlined and cool as possible in the Italian heat.

Riding steady: The heiress seemed focused and determined

Although the Athina's personal fortune is not known, she is widely believed to be a billionaire.

In November last year she suffered a spinal injury when she fell from her horse, but she has since recovered and made a return to the sport

Relaxing: Athina took a break from the strenuous sport

At an earlier event in Spain on 1 September Athina was pictured chatting with her husband Brazilian Alvaro Alffonso de Miranda

Earlier the heiress arrived with her husband in a more casual look of workout shoes - but already had her riding boot socks on